1. Field of the Invention
This invention relates to a method and an apparatus for manufacturing a curved board such as a dielectric board with a three-dimensionally curved surface (like a semispherical surface) on which surface a great number of printed antenna elements are arranged.
2. Description of the Related Art
In the conventional case of manufacturing an array antenna, its dielectric board is formed by laminating flat dielectric layers and copper foil layers on each other and attaching them at high temperature under high pressure. The thus-formed flat dielectric board is curved in the next step.
Further, in the case of manufacturing a curved printed wiring board, various methods are now being used--a method for first etching a flat board, and then curving the board into a shape similar to part of a cylinder or a cone; a method for producing a curved board with a relatively low curvature, and etching the board in units of one local spot which corresponds to each element; or a method for designing a curved board divided into portions with relatively low curvatures, forming these divided portions of small flat boards, and attaching the flat boards to each other after subjecting them to an etching process, thereby forming a single large curved board.
In each of the above-mentioned methods, processing at high temperature and under high pressure is necessary to shape a board or to make a board with a multi-layer structure. High temperature and pressure may well cause a change in size of the board, which cannot be ignored in producing the board. As regards etching, in the method in which etching is performed spot by spot, the line width of a continuous line pattern, for example, is hard to accurately set if adjacent spots intersect each other.
Even if an allowable range of changes in size or variations in accuracy is set, it significantly narrows the range of allowable curved surface shapes or limits the performance of products, in particular, in the case of boards for a high frequency antenna. As a result, a desired curved surface shape is hard to select.